Why always include lnum, onum, pnum and tnum?

Design
1

(Sorry, not a Glyphs-specific question but I thought I’ll get the most well-founded answers here…)

In my font, the default figures are proportional lining, and it also includes .osf, .tosf and .tf variants (in other words, it has the four typical sets). This means that the onum and tnum features are necessary but lnum and pnum are superfluous and will never have any effect (except hacky scenarios like picking one.osf from InDesign’s glyphs panel, plus lnum active).

So, my question is: Isn’t it reasonable to omit lnum and pnum in this case? Will this have a (good or bad) effect on the UI of some applications? Will it make things clearer? Or, will it, on the contrary, confuse users (or software)?

2

I had a look at the fonts I have installed on my system and of those font files offering all four number styles:

  • 249 files had two or three of these features
  • 313 files had all four of these features

So, including all appears to be more common. Personally, I would omit the feature for the default style, but it’s interesting to see that so many fonts do not.

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3

It would be interesting to know how many of these fonts were produced with Glyphs :wink:

4

I don’t fully remember but there was something that Adobe apps liked it better when all four features were there.

5

What Georg says: when I looked into this the last time (ages ago, I admit), some algorithms for building the labels in their OT substitution UI had issues if you didn’t have the superfluous features.

I remember the Adobe glyph picker tries to be smarter: it will insert the character and apply the reverse-engineered OT feature. It would fail if the OT features were set up in an unexpected way. IIRC adding all possible features helped.

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